It is established that the principal surface active components of lung surfactant, which lines the alveolar surface, are synthesized and secreted by the alveolar type II epithelial cell. The purpose of this research is to investigate the biochemical details of the synthesis of surfactant lipid and protein components and surfactant secretion in adult rat lung alveolar type II epithelial cells in primary culture. This cell model, now established, will be used to study the pathway, rate-limiting steps and control points of disaturated phosphatidylcholine and phosphatidylglycerol synthesis and related protein components in the type II cell and its subcellular organelles. These studies will be carried out in type II cell cultures derived from lungs of normal as well as diabetic rats in order to further define the role of insulin in surfactant production and type II cell metabolism. Isolated soluble, microsomal, Golgi, lamellar body and plasma membrane fractions of this purified cell preparation will be used to determine the sites, pathways of synthesis and enzymatic activities of key enzymes involved in surfactant production. As well, rate-limiting enzymes will be identified and their mode of regulation investigated. Secretion of surfactant material will be studied to determine the controlling factors including the involvement of alpha- and beta-adrenergic and/or cholinergic agonists and cyclic nucleotide mediation of this process. The results of these studies will further define the specific key and rate-limiting steps and control factors in surfactant synthesis in the normal and diabetic state so that targeted efforts may be made to correct defects in surfactant production in patients with respiratory distress syndrome.